This invention relates generally to a vibratory compactor machines and, more particularly, to an infinitely variable amplitude and frequency vibratory mechanism.
Vibratory compactor machines are commonly employed for compacting freshly laid asphalt, soil, and other compactable materials. For example these compactor machines may include plate type compactors or rotating drum compactors with one or more drums. The drum type compactor functions to compact the material over which the machine is driven. In order to compact the material the drum assembly includes a vibratory mechanism including inner and outer eccentric weights arranged on a rotatable shaft within the interior cavity of the drum, for inducing vibrations on the drum.
The amplitude and frequency of the vibratory forces determine the degree of compaction of the material, and the speed and efficiency of the compaction process. The amplitude of the vibration forces is changed by altering the position of a pair of weights with respect to each other. The frequency of the vibration forces is managed by controlling the speed of a drive motor in the compactor drum.
The required amplitude of the vibration force may vary depending on the characteristics of the material being compacted. For instance, high amplitude works best on thick lifts or harsh mixes, while low amplitude works best on thin lifts and soft materials. Amplitude variation is important because different materials require different levels of compaction. Moreover, a single compacting process may require different amplitude levels because higher amplitude may be required at the beginning of the process, and the amplitude may be gradually lowered as the process is completed.
Conventional vibratory compactor machines are problematic in that the amplitude and frequency of the vibration force can only be set to certain predetermined levels, or the mechanisms for adjusting the vibration amplitude are complex. One such vibratory mechanism is disclosed in U.S. Pat. No. 4,350,460 issued to Lynn A. Schmelzer et al. on Sep. 21, 1982 and assigned to the Hyster Company.
The present invention is directed to overcome one or more of the problems as set forth above.
According to one aspect of the invention a vibratory mechanism is provided that includes a first eccentric weight and a second eccentric weight being coaxially rotatable with the first eccentric weight. A first motor is connected with the first eccentric weight and a second motor is connected with the first second eccentric weight. One of the first and second motors is operable to change a phase difference between the first and second eccentric weights.
According to another aspect of the invention a method for adjusting the amplitude of a vibratory mechanism is provided. The vibratory mechanism includes first and second eccentric weights, a first motor connected to the first weight and a second motor connected to the second weight respectively via output shafts. A first driving step includes driving the first and second motors at the same speed and a second driving step includes driving one of the first and second motors, at a desired time, faster than the other motor to change a phase difference between the first and second eccentric weights in order to change a vibration amplitude.